always keep you blades very sharp. dull blades can damage the grass due to tearing the leaf blades
make sure you have plenty of gas before you start a job, there is nothing worse when your customer is sitting on their front porch and your mower runs out of gas and you have to leave it in their yard to make a quicl trip to the gas station.
wear long pants when you weed eat, or count on keeping tweezers to pick rocks or glass out of your legs